A mobile station establishes communications mainly in a direct mode and in a transfer mode. In the transfer mode, different mobile stations establish communications through a transfer device (a base station or a transfer station), and proper timeslot synchronization between a mobile station which triggers communications and the transfer device is essential to establish correct communications between different mobile stations. For example, timeslots of the transfer device includes timeslot 1 and timeslot 2 (the timeslot number may be user-defined, and the number of the timeslots of the transfer device is determined based on an applied communication standard), and timeslots available for the mobile station are timeslot 1 and timeslot 2 (the timeslot number may be also user-defined) respectively. If a preset synchronization rule is that timeslot 1 of the transfer device is synchronized with timeslot 1 of the mobile station, and the mobile station distributes timeslot 1 as a communication timeslot, other mobile stations operating at timeslot 1 may properly receive and analyze a signal only in a case that the mobile station transmits information at timeslot 1 and the transfer device transfers the information at timeslot 1. Similarly, if a preset synchronization rule is that timeslot 2 of the transfer device is synchronized with timeslot 2 of the mobile station, and the mobile station distributes timeslot 2 as a communication timeslot, other mobile stations operating at timeslot 2 may properly receive and analyze a signal only in a case that the mobile station transmits information at timeslot 2 and the transfer device transfers the information at timeslot 2.
In current DMR and PDT standards, a method for establishing communications between the mobile stations based on a transfer mode is defined as follows.
When the mobile station which triggers a communication service (referred to as the mobile station) communicates with other mobile stations via a transfer device, the mobile station directly transmits control information and service information to the transfer device, where the control information is mainly used for the transfer device and the other mobile stations to obtain a service type, and to get ready for the communications corresponding to the service type. The transfer device directly transfers the service information after receiving the service information. When transferring the service information, the transfer device only transfers the service information at a currently default operating timeslot, since the transfer device does not know and cannot obtain the timeslot used by the mobile station.